A century of weather records show there's no escape in Louisville from the fingerprints of climate change, as local temperatures climb and seasons are altered, research at the University of Louisville has found.

Experts warn of longer smog seasons and more health risks from heat, insects and flooding.

While the weather has its own natural cycles and variability, U of L research led by geography and geosciences professor Keith Mountain has come to a troubling bottom line: It's been getting warmer and it will likely keep getting warmer - driven mostly by rising low temperatures. And the rate of warming, which has been speeding up over the last 40 years, seems to be a little faster than anticipated.

"The temperature projections for Louisville are in line with and actually are greater than the rates of change and temperature increase as predicted (by climate scientists for) North America," said Mountain. "They may well reflect the impact of the now-recognized urban heat Island that has been observed for Louisville."

He was referring to other research out of Georgia Tech that identified Louisville's urban heat island - the difference between city temperatures and surrounding rural areas - as among the fastest growing in the country.

Still, Mountain said, climate change also appears to be at play with Louisville fitting into the overall pattern that scientists are seeing as human activities have pushed heat-trapping atmospheric carbon dioxide to levels not experienced in at least hundreds of thousands of years. "The overall consensus is that these (hemispheric) changes are not taking place uniformly throughout the year but are driven by changes in certain months, notable the spring and the fall seasons," Mountain said. "This is definitely the case for Louisville."

This area's early November hot spell, which twice broke all-time Louisville high-temperature marks for the month, could be part of what's in store, said Mountain, a climate scientist who has trekked to some of the most remote corners of the world to document the retreat of glaciers and polar ice. Warm weather is arriving earlier in the year, and lasting longer into the autumn, he said.

For the last decade, Mountain and his students have been compiling and studying Louisville weather data. This year, they updated the analysis with additional temperature and precipitation records dating to 1917, adding 40 years of data to an earlier 60-year look that reached similar conclusions.

Using observed data and statistics, and looking at three different time periods, Mountain's new work also makes predictions of weather trends out to 2050. It finds Louisville is likely to continue to get warmer and wetter.

Making the best of it

As this fall's Indian summer lingered into November, people in the Louisville area were taking advantage of the unseasonably warm autumn weather.

Many bicycle riders, for example, put their equipment away when it gets cold. But plenty were still out on the roads this month, said Louisville Bicycle Club President Andy Murphy.

SDF ties all time record high for November... 85 degrees... that was just set on Tuesday November the 1st..

Some club group rides that draw dozens of people in summer were still attracting large crowds with temperatures in the mid-80s and mid-70s. "It's just warmer," Murphy said, adding that the November heat felt wrong. "We can't be doing the planet any good."

Decadal rate of change, through 2050, from three different starting points(Photo11: Piktochart)

Kayaker Diann LoGuidice of Oldham County said recent warmth encourages people to get away from television and go outside. She said late October and November warm water and air made her frequent paddling more pleasant.

"There's a lot of doom and gloom about climate change," she said. "We have to live with it, so we might as well take advantage of it when we can."

That temperature changes so far and expected to occur over the next 35 years are a matter of a few degrees, which may not seem like a lot.

And Mountain said winter and snow won't be going away, adding that Mayor Greg Fischer better not get rid of the city's snow plows.

But he said the onset of a slightly warmer winter, particularly in relation to the minimum temperatures, means that the ground does not freeze as often or to typical depths. "All aspects of biological life can be expected to begin earlier and last longer affecting the environmental stability that we have come to expect," he added.

Louisville's sustainability chief, Maria Koetter, said she welcomes the U of L research. A city-commissioned study completed earlier this year found that heat contributed to the deaths of about 86 area residents in the scorcher summer of 2012, concluding that taking steps to cool Louisville's hot spots could save lives, money and improve living conditions for hundreds of thousands.

"What we can do is be ready from a preparedness standpoint," she said, adding that the city expects to launch a cool-roof incentive program and is trying to increase its tree canopy.

More ticks, mosquitoes

The U of L study found that we are getting about 7.5 more inches of rain every year now compared to a century ago. Other research by the Metropolitan Sewer District has found storms are getting more intense, raising concerns about the city's aging flood protection system.

A longer ozone season in a region that's long struggled with smog will exacerbate health problems for people with respiratory illnesses like asthma, COPD, emphysema and bronchitis, said U of L associate professor of geography and geosciences Carol L. Hanchette, whose research interests include health disparities.

More heat can also mean more heat exhaustion.

University of Louisville professor Keith Mountain.(Photo11: Photo courtesy of U of L.)

And warmer temperatures and more rain can extend the mosquito season, allowing the types of mosquitoes that spread the West Nile and Zika viruses to thrive, she said.

Ticks will likely get more weeks to bite into people and animals. "They are like little septic tanks they carry so many diseases," such as Lyme disease and Rocky Mountain Spotted Fever, she said.

Ozone also harms plants, so they find themselves having to repair that damage instead of growing as much, said U of L professor Margaret Carreiro, an ecologist in the biology department who teaches courses on climate change.

Invasive species like Asian bush honeysuckle and vines like winter creeper and English Ivy that smother or strangle native plants in large swaths of local parks and along highways thrive with the longer growing seasons, she said.

Decadal rate of change, through 2050, from different starting points(Photo11: Piktochart)

And she said she has observed how more intense rains have washed way huge volumes of valuable top soil.

Because gasses from burning fossil fuels destabilizes the climate system, she said, "We can also expect more unpredictable weather." One example, she said, is that polar vortex that's shown up in recent years, when a normal wintertime vortex of really cold air spinning around the top of the world weakens and dips into our area, ironically causing a deep freeze amid a background of general warming.

Climate change, she said, "is like this train that is coming down the track, but we are just beginning to experience it in a way that’s recognizable to the public."

Reach reporter James Bruggers at 502-582-4645 and at jbruggers@courier-journal.com.

Key findings:

The average annual maximum temperature has increased about 2 degrees, up from 65.4 degrees in 1917 to 67.3 in 2015. By 2050, that could rise anywhere from another 0.6 degrees to 3.1 degrees from 2015, for a possible total increase of between 2.5 and 5 degrees from 1917 to 2050.

The average annual minimum temperature increased 1.4 degrees from 46.6 degrees to 48 degrees between 1917 and 2015. But because temperatures have been rising faster in recent decades, especially the low temperatures, by 2050 the low temperatures could go up as much as 5 degrees more from 2015, for a possible total increase of between 2 and 6.5 degrees from 1917 to 2050.

It’s heating up earlier and staying warm later into the year. March, April, May and into June are seeing the greatest rate of change, followed by August, September and October.

April's average maximum monthly temperatures reflect an increase of between about a half degree to 1 degree per decade. That means it could be as much as 3.5 degrees warmer than currently for April.

For April, the average monthly low average temperature is rising nearly 1.5 degrees per decade. That means in 2050 it could be as much as 4.5 degrees warmer than now. For May, the average low temperature rise by 5 degrees in 2050.

Annual precipitation went up from about 40 inches per year in 1917 to 47.5 inches in 2015; it might increase another 5 or 6 inches by 2050.

Source: U of L Professor Keith Mountain

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In his first heat management report, Louisville Mayor Greg Fischer called on residents and business owners to take steps to improve the livability of Louisville by reducing heat.
Frankie Steele, Special to CJ